1. Field of the Invention
The present invention relates to a graphic editing apparatus and method. More particularly, this invention is concerned with a graphic editing apparatus and a graphic editing method both for creating or editing graphics on a display unit using a computer, wherein a graphic can be easily changed in position, shape, or state and delineated in a screen on the display unit with the passage of time or the change in value of an attribute.
2. Description of the Related Art
In the past, a graphic processing system based on a computer has handled a moving graphic such as an animated image according to a method in which a position of a graphic on a display unit at each time in stant is described using a predetermined script or a method in which all the positions or shapes of a graphic at respective time instants are designated independently.
According to the former method, the relationships between the position of a graphic and the time instant must be expressed as equations and position change information must be designated. It is therefore hard to determine the relationships between the time instant and position of a graphic during creation or editing. In particular, creating or editing a plurality of varying graphics is very hard to do. It is also hard to designate finely-varying states. Especially, editing work for varying a plurality of graphics simultaneously is very complex because time instants that are turning points of variations must be consistent among graphics.
In a method in which all the shapes of a graphic varying time-sequentially are designated at respective time instants, a position and shape of a graphic must be delineated in every screen sent at each time instant (hereinafter, a frame). An enormous amount of labor is required for creation or editing. After creation or editing is completed, (1) when a graphic is to be moved more quickly or slowly, all frames must be re-edited. Thus, correction is hard to do. (2) When time instants at which graphics vary synchronously are to be modified, all graphics in frames concerned must be re-edited. Thus, correction is hard to do.
When a conventional method is adopted, it is hard to edit not only a graphic varying time-sequentially but also a graphic varying depending on the value of a certain attribute. For example, when water is poured into a guitar-shaped vase, the water level in the vase rises with an increase in an amount of water. The rate at which the water level rises depends on the cross-sectional area of the vase. Even when the amount of water increases constantly, the speed at which the water level rises is not constant. For editing a graphic varying depending on the value of an attribute or the amount of water, the water level had to be described with complex equations or the water level had to be changed frame by frame in the past.
Assuming that an image of a scenery of sunset is edited, the colors of mountains and trees differ before and after sunset. The changes in these graphics must be synchronized with one another. When the time instant of sunset is to be changed, re-editing is required to change the colors of the individual graphics time-sequentially. In prior arts, complex work is required to edit such graphics synchronously with the passage of time.
The graphic processing system based on a computer offers various editing facilities for moving a graphic to another position, stretching or shrinking the graphic in a particular direction, enlarging or reducing the graphic, and rotating the graphic after displaying the graphic created on a display unit.
In the past, when these editing facilities were employed, an editing operation had to be designated to indicate what kind of editing was to be performed by switching edit modes using an icon menu or a command and then all points required for the editing operation had to be designated.
For example, when a certain graphic is to be rotated, first, an operation of "rotation" must be selected. A point acting as a rotation center is then designated. Thereafter, an angle of rotation is entered. When a square graphic is to be deformed to produce a rectangle, the square is deleted, and then a rectangle is created newly. Alternatively, "stretch/shrink deformation" is selected, and then it is designated which portion should be stretched or shrunken to what extent in which direction.
After a graphic is rotated once, when editing the graphic is completed, if an attempt is made to execute the same rotation, the previous sequence including a step of designating a point serving as a center must be repeated.
In a conventional graphic editing sequence, various editing operations must be designated in advance, and then a graphic to be deformed and a magnitude of deformation must be specified. The sequence is complex and time-consuming.
In the graphic processing system based on a computer, a plurality of graphics created independently on the display unit must sometimes be correlated with one another and handled as a single graphic. This correlating is required, for example, when a graphic of a steering wheel of an automobile, a graphic of a body frame, a graphic of a saddle, a graphic of front wheels, and a graphic of rear wheels are created independently and combined together to compose a graphic of an automobile. The graphic of a steering wheel or body frame must be composed by combining graphics of parts.
In prior arts, when a plurality of graphics of parts are to be created with the locations of the parts held intact, the locations of the parts are placed in memory and divided into groups. A group is regarded as a single graphic. Deformation, rotation, or movement is executed relative to the whole of a group.
In the conventional methods, however, when it is required to deform a particular one of graphics belonging to a group, the group of graphics must be broken up to execute deformation. When a group is broken up, the positional relationships between the graphic and the other graphics are destroyed. During the deformation, an editor must deform or move the other graphics.
For example, when the graphics of a handle bar and a body frame of a bicycle are correlated and grouped, these graphics are handled as a united graphic. It is therefore impossible to enlarge or reduce the handle bar alone. Enlargement or reduction cannot help involving the body frame. For enlarging the handle bar alone, the grouping of the handle bar and body frame is dissolved temporarily, and then the handle bar alone is enlarged. Thereafter, the position of the enlarged handle bar relative to that of the body frame is determined, and then the enlarged handle bar and body frame must be grouped again.